Silicon on insulator (SOI) applications are commonly utilized where a high degree of noise isolation or low signal loss is required. In such SOI applications, a conducting inversion layer is typically present at the interface between a base oxide and a high resistivity handle wafer. Resistivity requirements imposed by active devices within SOI applications also typically require a top silicon layer having a much lower resistivity than the high resistivity handler wafer. The combination of a low resistivity top silicon layer and an inversion layer at the base oxide-handle wafer interface results in a lossy, non-linear network that degrades isolation and linearity of SOI applications at high frequencies and power levels.
SOI applications have also employed annular isolation trenches in an attempt to reduce RF noise and increase isolation. However, such annular isolation trenches typically provide insufficient mechanical support around the circumference of the active areas being isolated, resulting in SOI substrates that are more prone to collapse.